Catalytic dissolution of two Turkish lignites in tetralin under nitrogen atmosphere: effects of the extraction parameters on the conversion

Two Turkish lignites were extracted with tetralin in a batch autoclave under nitrogen atmosphere. Fe2O3, Mo(CO)6, MoO3 or Al2O3 were used as the added catalyst. The isothermal extraction temperatures ranged from 325 to 425°C, the starting nitrogen pressure ranged from atmospheric to 5 MPa, the isothermal extraction periods ranged from 0 to 120 min. After removal of char and solvent, the remaining products were separated into three fractions: preasphaltenes (benzene insolubles), asphaltenes (benzene soluble, n-pentane insolubles) and oils (n-pentane solubles) by successive extractions with benzene and n-pentane. The variations in the conversions and soluble product compositions were investigated with respect to the extraction conditions. The results indicate that the conversions of the lignites are low below 350°C but high over 375°C. The catalysts enhance mainly the oil formation, and the catalytic activities of Mo(CO)6 and Fe2O3 are higher than the others. Lignite-impregnated catalysts show higher reactivity than the physically mixed catalysts. Increasing the extraction time and temperature affects the total conversion and soluble product composition. The gaseous product formation increases with the time at temperatures of 400°C and above.